Copies of the Guardian newspaper are displayed at a news agent in London August 21 2013. Photo: Reuters

The Guardian has agreed with the New York Times to give the U.S. newspaper access to some classified documents leaked by former National Security Agency contractor Edward Snowden, both papers said on Friday.

In a brief story posted on its website, the Guardian said it "struck a partnership" with the Times after the British government threatened the Guardian with legal action unless it either surrendered or destroyed files it received from Snowden about Government Communications Headquarters - Britain's equivalent of NSA.

"In a climate of intense pressure from the UK government, the Guardian decided to bring in a US partner to work on the GCHQ documents provided by Edward Snowden. We are working in partnership with the NYT and others to continue reporting these stories," the British newspaper said in a statement.

"We don't usually comment on our reporting before publication, but in this case we will make an exception since it is already public. The Times is reporting on material from The Guardian as well as other matters related to Edward Snowden," the Times quoted her as saying.

A source familiar with the matter said the partnership deal had been struck several weeks ago and that Abramson was personally involved in negotiating it.

The website Buzzfeed reported that Scott Shane, a Times reporter who covers national security and intelligence, was working on a series of stories expected to be published next month jointly with the Guardian.

The Guardian said in its story that its partnership with the Times would enable it to "continue exposing mass surveillance by putting the Snowden documents on GCHQ beyond government reach."

It said Snowden, who disclosed documents on U.S. internet and phone surveillance programs in June and has obtained asylum in Russia, was aware of the deal.

The Guardian's editor, Alan Rusbridger, revealed earlier this week that under the supervision of representatives of GCHQ, Guardian staffers had destroyed computer equipment containing Snowden files after the newspaper was threatened with possible legal action by senior British government officials.

Rusbridger said he had put British officials on notice that copies of material which had been destroyed had been sent outside British government jurisdiction.

British authorities say they launched a criminal investigation this week following the temporary detention and questioning at London's Heathrow Airport of David Miranda, domestic partner of Glenn Greenwald, a Brazil-based Guardian writer who has led coverage of leaks from Snowden and communicated directly with the former NSA contractor.

British officials have said that Snowden's leaks have gravely damaged national security and could put lives in jeopardy if more secrets are disclosed.

The Times and the Guardian previously collaborated on stories related to alleged phone hacking by British tabloid newspapers and on coverage of secret U.S. military and diplomatic documents made available by U.S. Army soldier Bradley Manning to the WikiLeaks website.